The U.S. Postal Service’s plan to end Saturday mail delivery this summer could erase the equivalent of some 35,000 full-time jobs, according to an internal agency document obtained by Federal Times.

That figure is higher than the one officials cited last week. At a news conference, Postmaster General Pat Donahoe said that the reduction in work hours following the end of Saturday mail would be equal to about 22,500 full-time jobs. But in the unsigned document, titled “Background/Talking Points/FAQs” and dated this month, the Postal Service estimated the workload cut at 35,000 full-time equivalents, with most of the savings coming from the city delivery category.

In an email Monday, USPS spokesman Mark Saunders said that the agency is “working to define the employee impact,” which he put at between 20,000 and 25,000 FTEs. He did not explain the origin of the 35,000 figure. Many of the hours that will be cut are overtime, according to Donahoe.

The financially struggling mail carrier, which had a total of 523,000 career employees at the end of December, plans to manage the cuts through attrition, reassignments, reduced overtime and other means. Buyouts are on the table, but, at this point, reductions in force are not, according to the Postal Service.

Under the plan, already under fire from some members of Congress, Saturday mail delivery would end in early August, although package delivery would continue. The Postal Service predicts that the change will save $2 billion annually when fully in place.

At the National Rural Letter Carriers’ Association, spokesman Mike Uehlein was not familiar with the 35,000 number, but questioned the accuracy of the Postal Service’s projections. Out of some 113,000 rural carriers, Uehlein said Monday, about 43,000 are part-time, noncareer employees who deliver mail mostly on Saturday and during the week as substitutes for full-time carriers. All of those jobs could be eliminated, he said.

“A lot of these numbers are just conjecture,” Uehlein said. “They can’t find out until it actually happens how much business that they are going to lose.”

At the National Association of Letter Carriers, the union representing mail carriers in urban areas, a top official accused Donahoe of “purposefully low-balling the jobs impact.”

The 22,500 figure only covers the effect on the workload of city carriers, not rural carriers, clerks and mail handlers who will also be affected, Jim Sauber, NALC chief of staff, said in an email.

Lawmakers are set to take their first formal look at the Postal Service’s plan at a Senate Homeland Security and Governmental Affairs Committee hearing Wednesday morning.